Reliability (R) is the probability an item (e.g., system,
subsystem, or component) will perform its intended function with
no failure for a stated period of time (or number of demands or
load) under stated environmental conditions. Other words,
reliability is the probability an item will be in an uptime
state (i.e., fully operational or ready to perform) for a stated
mission.

Maintainability (M) is the probability a failed item will
be restored or repaired to a specified condition within a given
period of time. Other words, maintainability is the probability
an item in a downtime state will be returned to an uptime state
within a given period of time.

Availability (A), a function of Reliability and
Maintainability (R&M), is the probability a repairable item will
perform its intended function at a given point in time (or over
a specified period of time) when operated and maintained in a
prescribed manner. Other words, availability is the probability
of an item’s mission readiness, an uptime state with the
likelihood of a recoverable downtime state.

Ideally from an RMA Plan, the RMA team performs three major functions,
namely, (1) Design for RMA, (2) RMA verification, and (3) Analytical
physics. For specific RMA tasks
click here.